Mitt Romney rolled to primary victories in Virginia, Vermont and home-state Massachusetts on Super Tuesday, reaching for a decisive advantage over his persistent rivals in the most turbulent race for the Republican presidential nomination in a generation.

WASHINGTON — Mitt Romney rolled to primary victories in Virginia, Vermont and home-state Massachusetts on Super Tuesday, reaching for a decisive advantage over his persistent rivals in the most turbulent race for the Republican presidential nomination in a generation.

Former House Speaker Newt Gingrich countered with a home-field win in Georgia as the GOP contenders vied for the chance to take on Democratic President Barack Obama in November.

Romney also dueled Rick Santorum in Ohio, their second industrial-state showdown in as many weeks and the marquee matchup of the busiest night of the race.

Santorum and the fourth contender, Rep. Ron Paul, sought success elsewhere, with contests stretching across the country and more than 400 Republican National Convention delegates at stake.

Win or lose there, Romney said "I think we'll pick up a lot of delegates, and this is a process of gathering enough delegates to become the nominee and I think we're on track to have that happen."

There were primaries in Tennessee and Oklahoma as well as Virginia, Vermont, Ohio, Massachusetts and Georgia. Caucuses in North Dakota, Idaho and Alaska rounded out the calendar.

Gingrich's victory was his first since he captured the South Carolina primary on Jan. 21, and the former House speaker said it would propel him on yet another comeback in a race where he has faded badly over the past six weeks.

Obama, the man they hope to defeat in November, dismissed the almost-constant criticism of his foreign policy efforts and accused Republicans of "beating the drums of war" over Iran. "Those folks don't have a lot of responsibilities. They're not commander in chief," he said. Unopposed for the Democratic nomination to a second term, he stepped into the Republican race with a Super Tuesday news conference at the White House, then attended a $35,800-a-ticket fundraiser a few blocks from the White House

He later attended a $35,800-per-ticket fundraiser a few blocks from the White House.

In Georgia, Gingrich was gaining 48 percent of the vote in early returns, with Santorum at 24 percent and Romney close behind at 22 percent.

In Virginia, Romney had 59 percent and Paul had 41 percent. Santorum and Gingrich failed to qualify for the ballot.

Romney led in Vermont with 39 percent of the vote in early returns, with Paul gaining 27 percent and Santorum 24 percent.

Ohio was the day's biggest prize in political significance, a heavily populated industrial state that tested Rick Santorum's ability to challenge Romney in a traditional fall battleground. Georgia, Newt Gingrich's home political field, outranked them all in the number of delegates at stake, with 76, a total that reflected a reliable Republican voting pattern as well as population.

Romney, the leader in the early delegate chase, flew home to Massachusetts to vote and said he hoped for a good home-state win. Overall, he added, "I think we'll pick up a lot of delegates, and this is a process of gathering enough delegates to become the nominee and I think we're on track to have that happen."

He also took issue with Obama, saying, "I think all of us are being pretty serious" about Iran and its possible attempt to develop nuclear weapons.

Gingrich, hoping for a victory in Georgia, effectively acknowledged he had scant Super Tuesday prospects elsewhere. Instead, he was pointing to primaries next week in Alabama and Mississippi, and he told an audience, "With your help, by the end of next week we could really be in a totally new race."

The polls show the president's chances for re-election have improved in recent months, as the economy has strengthened, unemployment has slowly declined and Republicans have ripped into one another in the most tumultuous nominating campaign the party has endured since 1976.